Depends on your use case and also which ecosystem you are invested in. If you want a more customizable experience and don't mind handling a big phone on a daily basis I say go for the note 4. Amazing screen very potent camera. And expandable memory. Rocking a 64gb card myself. Total 96gb! Freedom compared to my 16gig iPhone 5!

If they are similarly priced and you do not have a huge investment in the iOS/Apple App Store ecosystem (music, apps, "all my friends are on Facetime", etc), then the Note 4 pretty much beats anything the iPhone 5 (the 6 is another discussion entirely) has to offer hands-down. Larger screen, much newer device, expandable memory, replaceable battery, S-Pen the lot.

The reasons to choose an iPhone 5 over a Note 4 are mostly going to be that you are heavily invested in the App Store, you are reluctant to give up Apple-proprietary communications systems like Facetime, or the Note 4 is just too big for your purposes/preferences. All are perfectly valid reasons.

That is a very good question. And since your in the Note 4 forums im going to suggest, oh i dont know, maybe the Note 4.
Removable battery, expandable memory, great display, SPEN and those functions if you choose to use them.